28,302 research outputs found
Hard core attraction in hadron scattering and the family of the Ds meson molecule
We study the discovered Ds(2317) at BABAR, CLEO and BELLE, and find that it
belongs to a class of strange multiquarks, which is equivalent to the class of
kaonic molecules bound by hard core attraction. In this class of hadrons a kaon
is trapped by a s-wave meson or baryon. To describe this class of multiquarks
we apply the Resonating Group Method, and extract the hard core
kaon-meson(baryon)interactions. We derive a criterion to classify the
attractive channels. We find that the mesons f0(980), Ds(2457), Bs scalar and
axial, and also the baryons with the quantum numbers of Lambda, Xi_c, Xi_b and
also Omega_cc, Omega_cb and Omega_bb belong to the new hadronic class of the
Ds(2317).Comment: 5 pages, 1 figure, 2 tables, contribution to the X International
Conference on Hadron Spectroscopy, HADRON 2003, August 31 - September 6,
2003, Aschaffenburg, German
The Theta+ (1540) as an overlap of a pion, a kaon and a nucleon
We study the very recently discovered (1540) at SPring-8, at ITEP
and at CLAS-Thomas Jefferson Lab. We apply the same RGM techniques that already
explained with success the repulsive hard core of nucleon-nucleon, kaon-nucleon
exotic scattering, and the attractive hard core present in pion-nucleon and
pion-pion non-exotic scattering. We find that the K-N repulsion excludes the
Theta+ as a K-N s-wave pentaquark. We explore the Theta+ as heptaquark,
equivalent to a N+pi+K borromean boundstate, with positive parity and total
isospin I=0. We find that the kaon-nucleon repulsion is cancelled by the
attraction existing both in the pion-nucleon and pion-kaon channels. Although
we are not yet able to bind the total three body system, we find that the
Theta+ may still be a heptaquark state.Comment: 5 pages, 3 figures, 1 table, contribution to the X International
Conference on Hadron Spectroscopy, HADRON 2003, August 31 - September 6,
2003, Aschaffenburg, German
Scale-dependent rigidity of polymer-ornamented membranes
We study the fluctuation spectrum of fluid membranes carrying grafted
polymers. Contrary to usual descriptions, we find that the modifications
induced by the polymers cannot be reduced to the renormalization of the
membrane bending rigidity. Instead we show that the ornamented membrane
exhibits a scale-dependent elastic modulus that we evaluate. In ornamented
lamellar stacks, we further show that this leads to a modification of the
Caille parameter characterizing the power-law singularities of the Bragg peaks.Comment: 4 pages, 2 figure
Identification of fullerene-like CdSe nanoparticles from optical spectroscopy calculations
Semiconducting nanoparticles are the building blocks of optical nanodevices
as their electronic states, and therefore light absorption and emission, can be
controlled by modifying their size and shape. CdSe is perhaps the most studied
of these nanoparticles, due to the efficiency of its synthesis, the high
quality of the resulting samples, and the fact that the optical gap is in the
visible range. In this article, we study light absorption of CdSe
nanostructures with sizes up to 1.5 nm within density functional theory. We
study both bulk fragments with wurtzite symmetry and novel fullerene-like
core-cage structures. The comparison with recent experimental optical spectra
allows us to confirm the synthesis of these fullerene-like CdSe clusters
Clustering and Correlations at the Neutron Dripline
Some recent experimental studies of clustering and correlations within very
neutron-rich light nuclei are reviewed. In particular, the development of the
novel probes of neutron-neutron interferometry and Dalitz-plot analyses is
presented through the example of the dissociation of the two-neutron halo
system Be. The utility of high-energy proton radiative capture is
illustrated using a study of the He(p,) reaction. A new approach
to the production and detection of bound neutron clusters is also described,
and the observation of events with the characteristics expected for
tetraneutrons (n) liberated in the breakup of Be is discussed. The
prospects for future work, including systems beyond the neutron dripline, are
briefly outlined.Comment: Invited contribution to a topical issue on Exotic Nuclei of Les
Comptes Rendus de l'Academie des Sciences Paris, Serie IV. 29 pages,11
figures (format RevTex preprint
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